package cn.ymjr.sys.util;

import org.apache.commons.codec.binary.Base64;
import org.bouncycastle.jce.provider.BouncyCastleProvider;

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.security.AlgorithmParameters;
import java.security.Key;
import java.security.Security;
import java.util.Arrays;

/**
 * @author tiny
 * @date 2019/7/16 16:30
 * @description
 */
public class AesCbcUtil {

    public static String decryptData(String encryptDataB64, String sessionKeyB64, String ivB64) {
        return new String( decryptOfDiyIV(Base64.decodeBase64(encryptDataB64), Base64.decodeBase64(sessionKeyB64), Base64.decodeBase64(ivB64) ) );
    }
    private static final String KEY_ALGORITHM = "AES";
    private static final String ALGORITHM_STR = "AES/CBC/PKCS7Padding";
    private static Key key;
    private static Cipher cipher;

    private static void init(byte[] keyBytes) {
        // 如果密钥不足16位，那么就补足. 这个if 中的内容很重要
        int base = 16;
        if (keyBytes.length % base != 0) {
            int groups = keyBytes.length / base + (keyBytes.length % base != 0 ? 1 : 0);
            byte[] temp = new byte[groups * base];
            Arrays.fill(temp, (byte) 0);
            System.arraycopy(keyBytes, 0, temp, 0, keyBytes.length);
            keyBytes = temp;
        }
        // 初始化
        Security.addProvider(new BouncyCastleProvider());
        // 转化成JAVA的密钥格式
        key = new SecretKeySpec(keyBytes, KEY_ALGORITHM);
        try {
            // 初始化
            cipher = Cipher.getInstance(ALGORITHM_STR, "BC");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    private static byte[] decryptOfDiyIV(byte[] encryptedData, byte[] keyBytes, byte[] ivs) {
        byte[] encryptedText = null; init(keyBytes);
        try {
            cipher.init(Cipher.DECRYPT_MODE, key, new IvParameterSpec(ivs));
            encryptedText = cipher.doFinal(encryptedData);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return encryptedText;
    }



    public static String decrypt(String encryptedData,String key, String iv, String encodingFormat)throws Exception{
        //被加密的数据
        byte[] dataByte = Base64.decodeBase64(encryptedData);
        //加密秘钥
         byte[] keyByte = Base64.decodeBase64(key);
        // 偏移量
        byte[] ivByte = Base64.decodeBase64(iv);
        //如果不足16位
        int base = 16;
        if (keyByte.length % base != 0) {
            int groups = keyByte.length / base + (keyByte.length % base != 0 ? 1 : 0);
            byte[] temp = new byte[groups * base]; Arrays.fill(temp, (byte) 0);
            System.arraycopy(keyByte, 0, temp, 0, keyByte.length);
            keyByte = temp;
        }
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");

        SecretKeySpec spec = new SecretKeySpec(keyByte, "AES");

        AlgorithmParameters parameters = AlgorithmParameters.getInstance("AES");

        parameters.init(new IvParameterSpec(ivByte));

        cipher.init(Cipher.DECRYPT_MODE, spec, parameters);// 初始化

        byte[] resultByte = cipher.doFinal(dataByte);
        if (null != resultByte && resultByte.length > 0) {
            String result = new String(resultByte, encodingFormat);
            return result;
        }
        return "";

    }
}
